Mechanisms of Ghrelin Secretion

 描述(申请人提供)：Ghrelin是一种促食欲、血糖调节和抗抑郁的多肽激素，主要来自分散在胃粘膜中的一组不同的Ghrelin细胞。当轻度限制热量摄入以刺激食物摄入和脂肪储存，以及严格限制热量摄入以防止危及生命的血糖下降时，其血浆水平会上升。在心理社会压力下，生长激素释放素水平也会升高，从而最大限度地减少应激导致的抑郁，并诱导食物奖励行为。Ghrelin作用的这些关键的生理和行为效应通过在长期热量限制或慢性心理社会应激下观察到的Ghrelin、Ghrelin受体和/或Ghrelin O-酰基转移酶缺乏症小鼠模型中观察到的低血糖和抑郁表型来强调。尽管Ghrelin在血糖动态平衡和对心理应激的协调反应中起着关键作用，但对Ghrelin分泌的调节机制知之甚少。这一建议的中心主题是在Ghrelin细胞水平上确定调节Ghrelin分泌的机制，重点是1-肾上腺素能受体(？1-AR)信号转导。这些实验的目的是确定ghrelin细胞内的？1-AR信号是否是ghrelin对卡路里限制的反应所必需的，ghrelin细胞？1-ars是否需要ghrelin细胞对慢性心理社会应激的适当分泌和情绪反应，以及是否如假设的那样，磷酸戊糖途径和ChREBP(碳水化合物反应元件结合蛋白)介导？1-ars和葡萄糖对ghrelin细胞分泌反应的影响。该提案将利用为研究和操纵Ghrelin细胞而开发的独一无二的技术和工具集合。这包括用于体外评估Ghrelin分泌的分散的胃粘膜细胞的原代培养系统、Ghrelin-Cre转基因小鼠，当与新的条件性1-AR和功能性ChREBP基因敲除系杂交时，Ghrelin-Cre转基因小鼠允许选择性地从Ghrelin细胞中删除ç1-ARs和功能性ChREBP，以及Ghrelin-hrGFP转基因小鼠，报告Ghrelin细胞的位置并允许荧光激活的细胞对Ghrelin细胞进行分离。这种独特的小鼠品系和技术收集，以及随之而来的体内代谢和行为研究、体外分泌实验和其他评估，将使我们提出的关于Ghrelin分泌和Ghrelin对不同极端热量限制、食物摄入和心理社会压力的反应的假设得到严格测试。最终，计划中的研究有望促进我们对卡路里限制和慢性心理社会压力的协调生理和行为反应的理解，从而可能发现针对极端体重、慢性应激、抑郁症和进食障碍(如神经性厌食症)的新的治疗方式。

 DESCRIPTION (provided by applicant): Ghrelin is an orexigenic, glucoregulatory and antidepressant peptide hormone derived mainly from a distinct group of ghrelin cells dispersed throughout the gastric mucosa. Its plasma levels rise upon mild caloric restriction to stimulate food intake and fat storage and upon severe caloric restriction to prevent life-threatening falls i blood glucose. Ghrelin levels also rise following psychosocial stress, minimizing stress-induced depression and inducing food reward behavior. These key physiologic and behavioral effects of ghrelin action are emphasized by the hypoglycemic and depression phenotypes observed in mouse models of ghrelin, ghrelin receptor, and/or ghrelin O-acyltransferase deficiency upon exposure to prolonged caloric restriction or chronic psychosocial stress. Despite critical roles fo ghrelin in glucose homeostasis and the coordinated response to psychosocial stress, relatively little is known about the mechanisms regulating ghrelin secretion. The central theme of this proposal is to identify mechanisms mediating ghrelin secretion at the level of the ghrelin cell, with a focus on ß1-adrenergic receptor (ß1-AR) signaling. The experiments have been designed to determine if ß1-AR signaling within ghrelin cells is required for the ghrelin response to calorc restriction, if ghrelin cell ß1-ARs are required for appropriate ghrelin secretory and mood responses to chronic psychosocial stress, and if the pentose phosphate pathway and ChREBP (carbohydrate response element-binding protein) mediate the effects of ß1-ARs and glucose on ghrelin cell secretory responses, as hypothesized. The proposal will utilize a one-of-a-kind collection of techniques and tools developed to study and manipulate the ghrelin cell. This includes a system for primary culture of dispersed gastric mucosal cells with which to assess ghrelin secretion ex vivo, ghrelin-Cre transgenic mice which permit selective deletion of ß1-ARs and functional ChREBP from ghrelin cells when crossed with novel conditional ß1-AR and functional ChREBP knockout lines, and ghrelin- hrGFP transgenic mice that report on the location and allow for fluorescent-activated cell sorting of ghrelin cells. This unique collection f mouse lines and techniques and the accompanying in vivo metabolic and behavioral studies, ex vivo secretion experiments, and other assessments will allow our proposed hypotheses regarding ghrelin secretion and the ghrelin response to different extremes of caloric restriction, food intake and psychosocial stress to be rigorously tested. Ultimately, it is hoped that the planned studies advance our understanding of the coordinated physiologic and behavioral responses to caloric restriction and chronic psychosocial stress so that new treatment modalities for extremes of body weight, chronic stress, depression, and eating disorders such as anorexia nervosa may be uncovered.